Yes, GENU is a Scrabble word!

Letter values in Scrabble US: G 2, E 1, N 1, U 1.

Is it a valid word?

GENU is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

hinge joint in the human leg connecting the tibia and fibula with the femur and protected in front by the patella

Also: knee joint, human knee, articulatio genus.